Biocatalytic ester synthesis in ionic liquid media

Ionic liquids have shown potential as green reaction media compared with organic solvents, mainly due to their lack of vapour pressure. In non‐aqueous enzymology, ionic liquids are opening up new fields. The advantages of using ionic liquids over the use of organic solvents as reaction medium for biocatalysis include enhancement of enzyme activity, stability and selectivity. In this work, the enzymatic synthesis of esters in ionic liquids has been extensively reviewed. Numerous examples of the application of ionic liquids as reaction medium for the enzymatic production of esters have been included. The effect of the nature of the ionic liquid on activity, selectivity and stability of enzymes which catalyze esters synthesis has been carefully analysed. Innovative reaction methodologies for the biosynthesis of esters, including ionic liquid/supercritical carbon dioxide biphasic systems and the integrated reaction/separation processes using supported liquid membranes based on ionic liquids have been revised. Copyright © 2010 Society of Chemical Industry     

Novel Process Options for Application of Zeolites in Supercritical Fluids and Ionic Liquids

Supercritical fluids and ionic liquids offer attractive opportunities for modifying and applying zeolites as adsorbents and catalysts. After a brief introduction to the most important properties of these solvents, examples of zeolite applications in supercritical fluids and ionic liquids from the recent literature are discussed. Particular emphasis is put on the influence of reaction media on the processes occurring in the zeolitic pore systems, e.g., during shape‐selective conversions in zeolite catalysts. The present potential and future challenges for the application of zeolites in supercritical fluids and ionic liquids are identified. Most attractive process options arise from a combined use of both ionic liquids and supercritical fluids in integrated reaction schemes.     

离子液体支撑液膜的研究及应用进展

回顾了目前为止离子液体支撑液膜的制备方法、离子液体结构、支撑膜结构对离子液体支撑液膜稳定性的影响因素,介绍了其在有机物分离、气体分离、分离反应耦合方面的应用。由于传统的单元操作很难满足污染和对过程集成的要求,对离子液体支撑液膜在未来实现清洁生产的发展方向进行了展望。     

Heterogen katalysierte Herstellung von Furfural aus Xylose

The results of the dehydration of C₅‐raw material to obtain furfural via heterogeneous catalysis in water are discussed. Furfural has the potential to substitute fossil compounds on a large scale for polymers, solvents, fine chemicals and finally fuels. Industrial catalysts were reviewed and new catalysts were synthesized. The main difference to recent work is the abdication of supercritical fluids, organic solvents, phase modifiers and ionic liquids. With this also the contamination of the product is prevented and higher product qualities are obtained.     

室温离子液体在催化及有机反应中的应用

简述了室温离子液体在氢化反应、氧化反应和酯化反应等有机反应中作为催化剂和溶剂的应用。指出室温离子液体具有熔点低、有较宽的液态范围(大约300℃)、很强的溶解能力、良好的酸性并在很大的范围内可调、几乎没有蒸气压、高极性、较宽的电化学窗口和较好的热稳定性和化学稳定性等独特性能,可以重复使用。     

Optimization of the property profile of poly‐L‐lactide by synthesis of PLLA‐polystyrene–block copolymers

Diblock and triblock copolymers of poly‐L ‐lactide (PLLA) and polystyrene (PS) were synthesized and the mechanical properties of these copolymers studied. Free radical polymerization of styrene in the presence of 2‐mercaptoethanol as functional chain transfer agent produced mono‐functionalized PS‐blocks which were used as macroinitiators in the subsequent ring opening polymerization (ROP) of L ‐lactide to produce the diblock copolymers. Furthermore a α‐ω‐bishydroxyl functionalized PS‐block was synthesized by RAFT, which was then engaged as bifunctional initiator for the ROP of L ‐lactide to provide the triblock copolymers PLLA‐PS‐PLLA. Through the copolymerisation and high molar masses, it was possible to achieve an improved mechanical property profile, compared with pure PLLA, or the analogous blends of PLLA and PS. A weight fraction of PS of 10–30% was found to be the optimal range for improving the heat deflection temperature (HDT), as well as mechanical properties such as ultimate tensile strength or elongation at break. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Reactions and polymerization of hexa‐[3‐tert‐butyl‐4‐ hydroxyphenoxy]cyclotriphosphazene: A new method for the preparation of soluble cyclomatrix phosphazene polymers

Novel cyclomatrix phosphazene‐containing polyester polymers were synthesized through the reaction of a polyhydroxylated cyclotriphosphazene and a bifunctional acid chloride. To demonstrate the chemistry of the free hydroxyl of hexa‐[3‐tert‐butyl‐4‐hydroxyphenoxy]cyclotriphosphazene, nucleophilic displacement reactions were performed with both acetic anhydride and alkyl chlorides. This work compares favorably to literature data for the chemistry of hexa‐[4‐hydroxyphenoxy]cyclotriphosphazene, whose hydroxyl is not hindered by an adjacent substituent. The hindered site of hexa‐[3‐tert‐butyl‐4‐hydroxyphenoxy]cyclotriphosphazene was found to react with bidentate acid chlorides to yield new high polymers. The phosphazene‐containing polyesters were observed to have good solubility in polar organic solvents. Characterization of these new materials was performed using dilute solution laser light scattering techniques, thermal analysis, and NMR spectroscopy. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 242–251, 2001     

Effect of dimethyl sulfoxide on synthesis of thermoplastic cellulose‐Graft‐poly(l‐lactide) copolymer using ionic liquid as reaction media

In this study, ring‐opening graft polymerization of l ‐lactide onto cellulose was carried out homogeneously in ionic liquid (IL)/dimethyl sulfoxide (DMSO) co‐solvent as a reaction media. Through the effective control of high viscosity and steric hindrance caused by the interaction between the IL and the hydroxyl group of cellulose by adding DMSO as a co‐solvent, cellulose‐graft‐poly(l ‐lactide) (Cell‐g‐PLLA) copolymer with higher substitution efficiency was successfully prepared, at relatively low concentration of l ‐lactide. The maximum values of molar substitution, degree of lactyl substitution, and degree of polymerization of poly(l ‐lactide) in the copolymer were 3.76, 1.74, and 2.16, respectively, determined by ¹H‐NMR. The prepared cell‐g‐PLLA copolymers showed thermal plasticization with a glass transition temperature of 155°C. In addition, the thermal processibility could be improved as the amount of grafted PLLA in the copolymer increased. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41331.     

Green solvents for green technologies

In many industrial processes, large quantities of volatile and flammable organic solvents are used in various reaction systems and separation steps defining a major part of the environmental and economic performance of a process. Accordingly, a growing area of research in the development of green technologies is devoted to designing new, environment‐friendly and tunable solvents the use of which would meet both technological and economic demands. Among proposed solvents, room temperature ionic liquids, supercritical and subcritical fluids and solvents from natural and renewable sources stand out as the most promising approaches for current solvent innovation. A brief overview of up‐to‐date knowledge regarding these solvents is presented herein, with special emphasis on their properties, applications and further perspectives as truly green industrial solvents. © 2015 Society of Chemical Industry     

Ionic polymers with tunable liquid‐crystalline properties

Side‐chain polyesters were synthesized from N‐octyl‐, N‐dodecyl‐ or N‐hexadecyl‐diethanolamine and succinic acid anhydride. These polyesters were then transformed into polyester hydrochlorides by protonation of the amino groups using different amounts of HCl (20–100 mol%). Above 60 mol% the reaction is not quantitative and a degree of protonation of up to 88% is obtained. The structures of the synthesized polyesters and their hydrochlorides were determined by ¹H nuclear magnetic resonance spectroscopy. The thermal properties of the synthesized polyesters and their hydrochlorides were also studied using differential scanning calorimetry in relation to the side‐chain length and the degree of polyester protonation. The polyester with octyl side chains and its hydrochlorides were amorphous liquids at room temperature, while the polyester and polyester hydrochlorides with hexadecyl side chains formed a smectic crystalline phase, S_mB, or its tilted analogues. The polyester with a dodecyl side chain was also an amorphous liquid at room temperature, while its hydrochlorides with various degrees of protonation were smectic liquid crystals, as determined by X‐ray diffraction. By simply varying the degree of protonation the liquid crystal isotropization temperature was increased from 32 °C to 82 °C. Copyright © 2011 Society of Chemical Industry     

An investigation into the degree and rate of polymerization of poly(methyl methacrylate) in the ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate

Room‐temperature ionic liquids (ILs), including 1‐butyl‐3‐methylimidazolium hexafluorophosphate, [bmim⁺][PF₆^?], were investigated as replacements for volatile organic compounds in the free‐radical solution polymerization of poly(methyl methacrylate) (PMMA). The latter was synthesized in benzene and [bmim⁺][PF₆^?] at 70 °C via a free‐radical process and the degree and rate of polymerization were compared based on the solvent used. The degree of polymerization was found to be five times higher in [bmim⁺][PF₆^?] than in benzene, while the rate of reaction was approximately four times faster in [bmim⁺][PF₆^?]. The results indicate the potential for using ILs to produce high‐molecular‐weight polymers and block structures based on the increased free‐radical stability in ILs. Copyright © 2004 Society of Chemical Industry     

Synthesis,characterization and catalytic activity of zinc complex for ring‐opening polymerization of lactide

In the present study, salicylaldimine zinc complex (Zn‐HMBED) was synthesized and its reactivity for the ring‐opening polymerization (ROP) of lactide was studied. The zinc complex was prepared by the reaction of zinc solution with one molar equivalent of salicylaldimine Schiff base ligand in methanol under a nitrogen atmosphere. Further, the complex was characterized by various spectroscopic methods, which showed tetrahedral geometry. X‐ray diffraction studies were used for the structure determination of the Schiff base. It was observed that the zinc complex is highly active towards the ROP of lactide. The rate of polymerization is heavily dependent on the initiator used. The zinc complex allows controlled ROP as revealed by the linear relationship between the percentage conversion and the number‐average molecular weight. Finally, a mechanism for the ROP of lactide is proposed by use of the above zinc complex. © 2016 Society of Chemical Industry     

Impact of hexafluoroisopropylidene on the solubility of aromatic‐based polymers in supercritical fluids

Three different supercritical fluids (SCF), CO₂, dimethyl ether (DME), and propane, are investigated as potential solvents for processing two lactide‐based terpolymers and two perfluorocyclobutyl (PFCB) aryl ether polymers. The repeat unit of the lactide‐based terpolymers consists of a 1:1:1 ratio of L ‐lactide, diglycidyl ether of bisphenol A (DGEBA), and, in one case, 4,4′‐hexafluoroisopropylidenediphenol (6F‐Bis‐A) and, in the other case, 4,4′‐isopropylidenediphenol (6H‐Bis‐A). The PFCB‐based polymers are synthesized from 1,1‐bis[4‐[(trifluorovinyl)oxy]phenyl]hexafluoroisopropylidene (6FVE) and from bis(trifluorovinyloxy)biphenyl (BPVE). For both classes of polymer the steric effect of the hexafluoroisopropylidene (6F) group reduces chain–chain interactions, disrupts electronic resonance between adjacent aromatic groups, and improves solubility. The two lactide‐based terpolymers do not dissolve in CO₂ or propane, but dissolve in DME. At room temperature the poly(lactide 6F‐BisA DGEBA) terpolymer dissolves at 700 bar lower pressure in DME compared to the poly(lactide 6H‐Bis‐A DGEBA) terpolymer. Although the 6FVE polymer dissolves in all three SCF solvents, pressures in excess of 800 bar are needed to dissolve this polymer in CO₂ and propane while 6FVE dissolves in DME at pressure below 150 bar. The other PFCB‐based polymer (BPVE) only dissolves in DME, again at low pressure, although BPVE drops out of solution as the system temperature is raised above ～40°C, whereas 6FVE remains in solution in DME for temperatures up to 90°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1736–1743, 2005     

Synthesis and characterization of carborane‐containing polyester with excellent thermal and ultrahigh char yield

A series of wholly carborane‐containing polyesters with high thermostability were successfully synthesized by the catalytic polycondensation of carborane diol monomers with carborane diacid chlorides. They can be used for the preparation of materials of high temperature resistant coatings and adhesive. The influence of solvent, reaction temperature, and reaction time on the molecular weight and yield of the polymers were studied. In comparison with the carborane‐free polyester, the carborane‐containing polyesters showed higher degradation temperature and char yield and lower degradation rate. The thermal gravimetric analyzer (TGA) curves indicate that the carborane group could effectively reduce the degradation rate of carborane‐containing polyesters, which give a char yield of exceeding 64% under air (47% under N₂) at 700 °C. Such data are superior to the carborane‐free polyester, which showed a low char yield of around 0.3% under air (5% under N₂) at the same condition. Moreover, the thermal transition mechanism of carborane‐containing polyesters was also studied. The FTIR spectra and TG‐FTIR analysis indicate that the carborane cage could react with oxygen to form BOB and BC linkages at elevated temperatures, which postpones the thermal decomposition of polyester and accounts for the high char yield. The newly prepared kind of high temperature polyesters have enormous technical and economic value, especially in the high temperature fields. They can be widely used as raw materials to prepare the high temperature resistant coatings or adhesives for automotive engine, aircraft and other equipments worked in high‐temperature environments. Under high environmental temperature, the good thermal stability is capable of keeping polyesters stable and expanding their service lives. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44202.     

Phase behavior of mixtures of ionic liquids and organic solvents

A corresponding-states form of the generalized van der Waals equation, previously developed for mixtures of an ionic liquid and a supercritical solute, is here extended to mixtures including an ionic liquid and a solvent (water or organic). Group contributions to characteristic parameters are implemented, leading to an entirely predictive method for densities of mixed compressed ionic liquids. Quantitative agreement with experimental data is obtained over wide ranges of conditions. Previously, the method has been applied to solubilities of sparingly soluble gases in ionic liquids and in organic solvents. Here we show results for heavier and more-than-sparingly solutes such as carbon dioxide and propane in ionic liquids.     

Progress in the Preparation of Functional and (Bio)Degradable Polymers via Living Polymerizations

This review presents the latest developments in (bio)degradable approaches and functional aliphatic polyesters and polycarbonates prepared by typical ring-opening polymerization (ROP) of lactones and trimethylene carbonates. It also considers several recent innovative synthetic methods including radical ring-opening polymerization (RROP), atom transfer radical polyaddition (ATRPA), and simultaneous chain- and step-growth radical polymerization (SCSRP) that produce aliphatic polyesters. With regard to (bio)degradable approaches, we have summarized several representative cleavable linkages that make it possible to obtain cleavable polymers. In the section on functional aliphatic polyesters, we explore the syntheses of specific functional lactones, which can be performed by ring-opening copolymerization of typical lactone/lactide monomers. Last but not the least, in the recent innovative methods section, three interesting synthetic methodologies, RROP, ATRPA, and SCSRP are discussed in detail with regard to their reaction mechanisms and polymer functionalities.     

Temperature‐sensitive membranes prepared by the plasma‐induced graft polymerization of N‐Isopropylacrylamide into porous polyethylene membranes

A temperature‐responsive polymer, poly(N‐isopropylacrylamide) (PNIPAAm), was grafted onto porous polyethylene membranes by a plasma‐induced graft polymerization technique. A wide range of grafting was achieved through variations in the grafting conditions, including the postpolymerization temperature, time, monomer concentration, and graft‐reaction medium. The active species induced by plasma treatment was proven to be long‐living via a postpolymerization time of 95 h. Different solvent compositions, that is, water, methanol, benzene, and water/methanol, were used as reaction media, and water showed a much higher polymerization rate than the organic solvents. Based on the hydrophilicity of the active species, a mechanism explaining the solvent effect in plasma‐induced graft polymerization was examined. Characterizations by scanning electron microscopy, X‐ray photoelectron spectroscopy (XPS), and micro Fourier transform infrared showed that the grafted polymers were located on both the outer surface and inside pores of the membranes. The XPS analysis also confirmed that the polar amide groups tended to distribute more outward when grafted PNIPAAm was in its expanding state than when it was in its shrinking state. Water permeation experiments showed that the permeability of the grafted membranes varied dramatically with a slight temperature change in the vicinity of the lower critical solution temperature (LCST) of PNIPAAm. The effective pore radii of the grafted membranes above and below the LCST could be depicted by Hagen‐Poiseuille's law. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3180–3187, 2003     

Artificial Neural Network modeling of solubility of supercritical carbon dioxide in 24 commonly used ionic liquids

Application of supercritical CO₂ for separation of ionic liquids from their organic solvents or extraction of various solutes from ionic liquid solvents have found great interest during recent years. Knowledge of phase behaviors of the mixtures of supercritical CO₂+ionic liquids is therefore drastic in order to efficiently design such separation processes. In this communication, Artificial Neural Network procedure has been applied to represent the solubility of supercritical CO₂ in 24 mostly used ionic liquids. An optimized Three-Layer Feed Forward Neural Network using critical properties of ionic liquids and operational temperature and pressure has been developed. Application of this model for 1128 data points of 24 ionic liquids show squared correlation coefficients of 0.993 and average absolute deviation of 3.6% from experimental values for calculated/estimated solubilities. The aforementioned deviations show the prediction capability of the presented model.     

Use of ionic liquids as ‘green’ solvents for extractions

This review summarizes recent applications of ionic liquids (ILs) as ‘green’ solvents in extractions of a variety of substances, including metal ions, organic and bio‐molecules, organosulfur from fuels, and gases. ILs could also be used along with another ‘green’ technology, supercritical fluid extraction (SFE), for a more effective separation of products from ILs. In addition to their environmentally‐benign feature, ILs have other favorable properties over organic solvents used for extraction, such as adjustable hydrophobicity, polarity and selectivity. Copyright © 2005 Society of Chemical Industry     

Biodegradable Polymers, 9. Technologically Relevant Aspects of Kinetics and Mechanism of Ring‐Opening Polymerization of L,L‐Dilactide

Poly(L ‐lactide) is manufactured by a cascade process comprising the fermentation of glucose substrate, oligomerization of L ‐lactic acid, cyclization depolymerization to L ,L ‐dilactide and ring‐opening polymerization of the cyclic diester. The process development requires detailed knowledge of kinetics, thermodynamics and reaction mechanism in all process stages. This paper aims to show the influence of micro‐ and macrokinetic factors on the course of the ring‐opening polymerization and the molecular parameters of the formed polyester. Monomer conversion and molecular weight of the polyester are determined by chemically active process parameters, like kind and concentration of catalyst and initiator, respectively, reaction temperature or presence of cocatalysts as well as by the intensity of mixing of the polymerizing melt. The highest polymerization rate is observed in presence of tin octoate, but this catalyst leads to a fast degradation of the formed polymer.